Last time I used some, called Plastikote "Hot Paint", I baked it in the oven at about 250 deg. C. for 3 hours. When I fitted the manifold, all the paint had fallen off within a few months. It sucked.
I found a tin of etch primer rated at 220 deg. C. I'm hoping this will be enough, and will help a high temperature top coat stick to the remaining galvanising.
Best wishes,
Chris